Variable volume wobble plate pump



Oct. 18, 1960 F. E. NoRLlN VARIABLE VOLUME WOBBLE PLATE PUMP Filed Oct. 29, 1956 United States Patent 2,956,501 VARIABLE VOLUME WOBBLE PLATE PUMP Francis E. Norlin, 'Chesterland, Ohio, assignor to Borg- Warner Corporation, Chicago, Ill., a corporation of Illinois Filed ct. 29, 1956, Ser. No. 618,855

6 Claims. (Cl. 10S-37) This invention relates to pumps and pump assemblies in which a plurality of pump cylinders are arranged in circular series parallel to each other and to the axis of the drive shaft, each of the cylinders having disposed therein a piston or plunger actuated by a cam or swash plate fixed on the shaft.

The pump assembly forming the subject matter of my invention is provided with means to Vary the displacement thereof, such means including means responsive to the discharge pressure of the pump assembly, and is further provided with means to select the maximum discharge pressure. Such means are desirable in pump assemblies which are constantly rotating, as for example, those used in aircraft installations and where the displacement requirements vary from a maimum to a zero value.

In particular, the aforementioned means to vary the displacement of the pump assembly includes a control or bypass pump means mounted in tandem with a main xed displacement pump, and a control valve means, the control pump means being operated by the discharge pressure from the main pump cylinders and under the control o-f the control valve means, which selects a relatively high fluid pressure -or a relatively low uid pressure for application to a means associated with the control pump means. The application of the fluid pressures will cause variance of the discharge pressure from the pump assembly between a maximum and zero value.

Therefore, the principal object of my invention is the provision of an improved variable displacement pump assembly.

Another object of my invention is the provision of an improved variable `displacement pump assembly of the type having a plurality of circularly arranged cylinders and pistons, and means responsive to discharge pressure to vary the displacement thereof.

A still further object of this invention is the provision of an improved variable displacement pump assembly of the type described having means responsive to discharge pressure to vary the displacement thereof, which means includes a control pump means.

Still another and further object of this invention is the provision of an improved variable displacement pump assembly of the type `described having means responsive to discharge pressure to vary the displacement thereof, which means includes a control valve means.

Still another object of this invention is the provision of an improved variable displacement pump assembly of the type described having means responsive to discharge pressure for varying the displacement thereof, which means includes a control pump means and a control valve means. Y

Another object of this invention is the provision of an improved variable displacement piston pump assembly having means associated therewith and responsive to discharge pressure for varying the displacement thereof which includes a control pump means and a 2 control valve means for controlling the operation of the control pump means.

Another and still further object of my invention is the provision of a pump assembly including a fixed dis- Still further an object of my invention is the provision of a pump assembly comprising a xed displacement swash plate pump together with a variable bypass pump and a control valve operating to vary the displacement of the assembly.

These and other features and objects of my invention will become apparent from the 'following description when taken with the accompanying drawing in which:

Figure l is a cross-sectional illustration of a variable displacement pump assembly of ya main pump, a control or variable bypass pump means and an associated control valve means, showing the pump assembly in its full displacement operation; and y v Figure 2 is a partial `cross-sectional illustration, similar to Figure l, but showing the pump assembly in its Referring now to the drawing, there is illustrated a main, fixed displacement pump P, a control or bypass pump means PC and `an associated control valve means V. The two pumps and the valve are disposed within a common housing 1% constructed of a plurality. of parts (not shown) in a well-known manner. The housing 10 is provided with a cylindrical cavity 11 having a pair of spaced shoulders 12 and 13, Iand receives complementary shaped, interlocking cylinder blocks 14 and 15 between the shoulders 12 and 13. u

The housing 10 is provided with an inlet passage 16 and an outlet passage 17, the inlet passage communieating with the cavity 11 and the outlet passage 17 communicating with an annular groove 18 formed within the cavity 11. Y

The cylinder block 14 is substantially annular in shape, and the cylinder block 15 is centrally bored to define, with a central opening in the block 14, aninlet cavity or chamber 19. The blocks 14 and 15 alsodeline a discharge cavity or chamber 20 adjacent the groove 18, as illustrated. Y

The cylinder block 15 is provided with a plurality of longitudinal bores or cylinders 21 therethrough (two shown, but usually nine are provided) each of which slidably receives a hollow piston or plunger 22,. The pistons 22 are reciprocated Within their respective cylinders by means of a cam or swash plate 23 received within the housing cavity 11. The cam or swash plate 23 is rotatably driven by means of a shaft 24 passing through an opening in the housing 10 and being suitably journalled therein by well-known bearings and journal means.

Each piston 22 comprises an elongatedl cylindrical member having open-ended cylindrical bore or cavity 25 and being provided transverse openings 26 joining the outer periphery and the bore 25. Each piston 22 is also provided with an enlarged terminal end 27 having a substantially semi-spherical indentation 28 therein for receiving a complementary shaped portion of akbearing shoe 29 which is slidable on the face of the cam or swash plate 23. Cooperating with the enlarged terminal portion 27 of each piston 22 is a piston return element 30 Patented oct. 1s, 1960 having forked portions 31 `fitting over each piston and being rockably supported at its center by means of a protuberance 32, rearwardly extending from and integral with the cylinder block 15. The function of return member should be obvious.

A oating valve means 33 is carried by each-of the pistons 22 so as to close the'open end thereof during its pressure or discharge stroke and comprises a valve member 34 adapted to seat on the open end of thepiston and being retained within the bore 25 by means of a snap 'ring 35 carried by ns 36 on the valve member 34 andslidable within a groove 37 formed in the walls of the lbore 25. y

An annular groove 38 is formed within the wall of "each cylinder 21 Vand communicates with the inlet cavity or chamber 19`by means of a passage 39 for the flow of inlet fluid to the bore 25 of the piston 22 by means of the transverse openings 26.

, Each cylinder 21 is provided with a discharge valve 40 located in the discharge chamber 20, and which comprises va valve member 41 resiliently urged toward seating engagement with a face of the block member 15 by means of a coil spring 42. Each valve member 41 is provided with a cylindrical stem portion 43 having an elongated opening 44 therethrough.

Eachv'alve stem 43 is Slidably received within a complementary shaped bore 4S formed in the block 14, which bore communicates with an enlarged, concentric bore 46. Each bore '46 Slidably receives a cylindrical piston or plunger 47 having a semispherical terminal end engageable by 'means of a plate-like member 48. The member '48 is provided -with a hub rockably supported on a hemispherical portion 49 of a piston element 50 and is retained spaced from the block 14 by means of protuberances S1 extending from and integral with the `block "14. The plate like member'48 is received within the housing cavity 11 and is provided with a plurality of spaced openings 52 for the passage of fluid from the inlet 16 to the inlet cavity or chamber 19.

The piston like member '50has a cylindrical portion Slidably received within a bore 53 formed in the housing communicating at one end with the cavity 11. The member 50 is provided with an open ended bore 54 to receive a coil spring V55 therein, the other end of which reacts againstfthe terminal end of the'bore53 to resiliently urge the member 50 to the position illustrated in Figure Y1, which corresponds to full displacement of the pump assembly.

The control valve means V comprises a shuttle member 56 slidable between certain -limits within spaced portions of a 4bore 57 formed within the housing '10, and having an enlarged terminal portion 58. Between the spaced portions of the ybore 57, the housing 10 is provided with enlarged communicating, concentric, cylindrical cavities 59 and 60, spaced by means of a communicating, concentric bore 61, the `purpose of which will be later described. The enlarged shuttle portion 58 is received within a communicating, concentric, bore 62 having a diameter greater than the bore`57 and which also receives a coil control Vspring 63 urging the shuttle upwardly, as illustrated in Figure l. The loading of the coil spring 63 may be varied by means of a slotted screw 64 acting through a spring retainer V65 received within the bore 62. The limits of movement of the shuttle v56 are determined, at-one end by the end of the bore 57, and at the other end by the control spring 63.

The upper-most portion of the bore 57 communicates with the `discharge passage V17 by means of a conduit- 66 having a restriction 67 therein; the cavity 59 communicates with the cavity 534 by means of a `passagettS; and the bore 62 communicates with the housing cavity 11 behind the cylinder -block 1S by means of --a passager-69.

The shuttle 56 is provided withfspaced grooves 70, 71, separated by -means of an enlarged cylindrical -portion 72 dened at opposite ends by conical surfaces. The

4 enlarged portion 72 is generally disposed within the bore 61.

Slidably disposed about the shuttle and contained within the cavities 59 and 60 are floating valve seats 73, 74, which are resiliently urged toward their seated positions by means of coil compression spring 7'5, 76, respectively. The shuttle 56 is provided with bores 77 and 78, the bore 77 communicating with the bore 57 at one end of the shuttle and with the grooves 71 closely adjacent the enlarged `central portion 72 thereof, and the groove 78 communicating with the bore 62 at the opposite end of the shuttle and with the groove 70 closely adjacent the enlarged central lportion 72 thereof. It will be noted that the portions of the bores 77 and 78 within the central enlarged portion 72 of the shuttle are angularly disposed and parallel to one another, but do not intersect.

The oating valve seats 73 and 74 are adapted to seat on the conical surfaces of the shuttle, previously described, but are limited in their resiliently urged movement 'by means of the walls joining the cavities 59 and 60 and the bo're 61, these walls acting as stops for the valve seats. Passage Vmeans 61a is provided in the control valve means V for fluidly interconnecting cavities 59 and 60 so that the cavities 59 and 60 remain in fluid communication regardless of 'whether either of the Valve seats 73 and 74 are disposed in engagement with the wall dened by the junctures of the bore 61 and the cavities 59 and 60.

Detailed operation The following description sets forth the operation of the pump assemblyand this operation will be described with reference, whenever possible, to one of the pair of the plurality of piston pairs, it being understood that the operation of all pistons in each of the two pumps is the same. In following the description, it must be remembered that displacement of lthe pump assembly will be varied by means associated therewith under the control of pump assembly dischargepressure.

Assuming the shaft 24 to be rotating, the cam or swash plate 23 joined thereto will also be rotating and cause the pistons 22 to be reciprocated within their respective cylinder bores 21 between their suction position (see the lower piston Figure l) and their pressure or discharge position (see the upper piston Figure l).

Inlet fluid will ow through the inlet passage 16, into the left end of the housing cavity 11, through the openings 52 and into the inlet cavity 19 uid will flow through the passages 39, into the grooves 33, through the openings 26, and to the bores 25 in the pistons 22. With the fluid flowing into the piston bore 25, the valve 34 associated with the piston will be unseated, as shown in the lower portion of Figure l, and uid will flow therearound to till the portion of the cylinder 21 unoccupied by the piston 22. Upon the pressure or discharge stroke of the piston, the trapped iiuid within the unoccupied position of the cylinder 21 will be placed under pressure, thereby causing the valve member 34 to seat on the open end of the piston bore 25, and closing tl-e communication between the cylinder and the inlet through the bore 25. When the uid reaches a pressure suicient to overbalance the spring 42, the discharge valve 41 will be unseated and allow the uid under pressure to be discharged to the discharge cavity 20 and into the discharge passage 17.

It must be noted that some of the fluid will pass through the central bore 44 of the discharge valve and react against the piston 47, tending to move the piston 47 to a position, such as shown in Figure 2. However, the force of the spring 55 acting against the member 50 provides an initial loading force to retain the member 48 in its Figure 1 position, so that initially the piston 47 will be retained in its Figure 1 position and allow the discharge pressure 'to start building up.

With discharge pressure iiowing through the discharge passage 17 to a point of utilization, a portion thereof will flow through the passage 66 and through its restriction 67, thereby providing a pressure equal to or related to discharge to flow within the bore 57, through the shuttle passage 77 and into the shuttle groove 71. Until the discharge pressure reaches the predetermined maximum value as selected by the screw means, the shuttle 56 will be held in the position illustrated in Figure 1 wherein the oating valve seat 73 is in its seated position isolating the groove 70. The floating valve seat 74 is prevented from being seated by means of the wall joining the bore 61 and the cavity 60. Therefore, uid flowing into the groove 71 will ow between the oating valve seat 74 and the conical surface of the shuttle 56, into the cavity 59, through the passage 68 and into the cavity 53, thereby reinforcing the force exerted on the member 50 by the spring 55 to retain the member 43 in its Figure 1 position, so as to provide the maximum displacement from the pump assembly.

Upon the discharge pressure reaching a value higher than that selected, the pressure within the bore S7 will act through the shuttle 56 and overbalance the spring 63, thereby causing the shuttle to move downwardly, so that the lower conical surface of the shuttle picks up the oating valve seat 74 and moves it from its stopped position. This action will allow the valve seat 74 to seat and effectively isolate the pocket 71. The valve seat 73 then will be resiliently urged to a stopped position spaced from its seat to allow communication between the cavity 59 and the groove 70.

The rluid pressure in the cavity 53 will then llow through the passage 68, into the cavity 59, into the groove 70, through the shuttle passage 7S and into the bore 62, from which it will ow through the passage 69 to the right-hand portion of the cavity 11 in the housing 10. Fluid escaping from the cavity 53 in this manner allows the piston member 50 to move back compressing the spring 55 as shown in Figure 2.

The only fluid pressure existing in the last-named portion of the cavity 11 is that due to uid leaking past the pistons 22 which pressure has a value of much less than discharge. The fluid in this portion of the cavity 11 or case pressure provides fluid `for the lubrication of the rotating parts of the pump.

Under these conditions, the fluid being placed under pressure in the cylinders 21 will then flow through the discharge valve bores 44 and into the cylinders 46, acting against the pistons 47 and moving them to a position such as illustrated in Figure 2. The member 4S will rock about its pivot, and cause the pistons 47 to be reciprocated within their respective cylinder bores 46. This operation effectively reduces the displacement of the pump assembly since each piston 47 will force uid back into its associated cylinder 21 upon the suction stroke of the piston 22 therein.

As the demands on the pump assembly vary `from maximum to zero, the pump and its controls will perform the cyclic operation just described, and it is to be noted that as the pressure applied to the shuttle 56 var-"ies, oil ow will be entering, leaving or trapped in the bore 53, thereby moving the piston S0 forward, backward, or holding it in some intermediate position. The position of the piston 50 determines the degree of rocking of the member 48. With this changing condition, the extent of the strokes of the pistons 47 will vary, so -as to provide a variable displacement ow from the pump.

The main pump P will always discharge a constant amount of uid, but with the combined operation of the main pump and the variable displacement bypass pump, -a variable displacement flow will be provided.

While I have described my invention in connection with one specic embodiment thereof, it is to be understood that this is by way of illustration and not by way of limitation and the scope of my invention is defined solely by the appended claims which should be construed as broadly as the prior l'ar-t will permit.

I claim:

1. In a pump assembly, the combination of :a housing having an inlet and an outlet; a first pump means in said housing adapted to pump fluid from said inlet through said housing fand out said outlet comprising a cylinder bore, an open-ended piston means received in said bore for movement between a suction position and discharge position, cam means to move said piston means between said positions, valve means operatively associated with said piston means and adapted to close the open end thereof upon movement of said piston means to its discharge position whereby to trap a quantity of uid within said bore and to discharge the iluid under pressure; a control pump in said housing and adapted to receive and discharge uid from said lirst pump means so fas to vary the displacement of said pump assembly, said control pump comprising a cylinder bore in alignment with the cylinder bore of said rst pump means, a piston member received in the last-named cylinder bore and adapted to be moved between an assembly zero displacement position and assembly maximum displacement position; and means to control and determine the position of said piston member including a control element and a control valvel means, said control element being movable and operatively associated with said piston member and having a pressure receiving chamber, said control Valve means being fluidly connected to said outlet and being so constructed and arranged to selectively apply and disapply pump assembly discharge pressure -to said chamber to move said control element and thereby said piston member to a position 0f higher pump `displacement `and allow said control element and thereby said piston member lto move to a position of lower pump displacement to thereby vary the displacement of said pump assembly.

2. In a variable displacement pump assembly, the combination of la housing having )an inlet and an outlet, a pair of cylinder blocks received in said housing and defining a discharge chamber in communication with said outlet, an aligned bore in each block, piston means in each bore, cam means for reciprocating said piston means in one of said bores to thereby pressurize fluid from said inlet, resiliently urged valve means in said chamber, passage means in said valve means fluidly communicating said bores, said passage means allowing a ow of iluid under pressure from said one bore to the other bore, :and means to vary lthe position of said piston means in the said other bore to determine the -amount of tluid that can llow into the said other bore to thereby determine the amount of uid that can flow past said valve means into said discharge chamber and to said outlet.

3. In a pump assembly, the combination of a housing having an inlet and an outlet, means defining a discharge chamber in communication with said outlet, at least a pair of aligned bores in said housing, piston means in each bore, cam means for reciprocating said piston means in one of said bores to thereby pressurize fluid from said inlet, resiliently urged valve means in said chamber, passage means in said valve means uidly communicating said bores, said passage means allowing a ow of fluid under pressure from said one bore to the other bore, means to vary Ithe position of the piston means in the said other bore to Idetermine the amount of uid that can flow into the said other bore to thereby determine the amount of uid that can ow .past said valve means into said discharge chamber and to said outlet, said piston varying means including a control valve means tluidly connected to said outlet and being so constructed and arranged to cause movement of the pis-ton means in the said other bore toward said resiliently urged valve means to raise the displacement of the pump assembly and to allow movement of the piston means in the said other bore away from said resiliently urged valve means to lower the displacement of the pump assembly.

4. In a pump assembly, the combination of a housing having 1an inlet and an outlet; a rst pump means in said housing adapted to pump flu-id from said inletthrough said housing and out said outlet comprising a plurality of circularly arranged lparallel cylinder bores, open-ended piston means `received in each .of said bores for movement between-a suction position-and adischarge position, cam means to move said piston means between said positions, valve means operatively `associated with each of said piston means and adapted to close .the open .ends thereof upon movement of said piston means to their discharge position whereby to trap a quantity of lluid within each of said-bores and to discharge the fluidunder pressure therefrom; avcontrol pump in said housing and adapted Vto receive and discharge fluid .from said tirst pump means so as to vary/the `displacement of said .pump assembly, said control pump comprising a plurality of cylinder bores in alignment with the `cylinder `bores of said rst pump means, a piston member received in each ofthe -last-namedcylinder ybores and adapted to be moved between an assembly zero displacement position and assemblymaximumdisplacement position; and means to control and determine the positions of saidrpiston members including a control element and a control lvalve means, said vcontrol element Ybeing movable andoperatively associated -with saidpistonmembers and having a pressure receiving chamber, said control valve means being liuidly connected to said outlet and being so constructed and arranged to selectively apply and disapply pump assembly discharge pressure to said chamber to move said control clement ,and thereby said piston members to a-position of higher pump displacement and allow said control element and thereby said piston members tomove-tovaposition-of lower pump displacement to thereby vary the displacement of said pump lassembly.

5. In a .pump assembly, thecombination of a housing having an inlet'and an outlet, a pair of cylinder blocks received in said housing and dening a discharge chamber in communication with -said outlet, a pluralityfof `aligned bores in each block, piston means received in each bore, cam-means for reciprocating the piston means in said bores in one of said blocks-to pressurize fluid from said inlet, Aresiliently urged Valve means for each bore in said one block received in said chamber, passage means in each of-said valve meanslfluidly communicating said respective `alignedbores, said-passage means allowing` a tlow of -uid under pressure from-theone 'aligned bore in said onevblock -to the aligned bore in the other block, means to vary-the positionsof the piston means control element having a pressure receiving chamber therein, and said control valve means being soconstrueted and` arranged lto ,selectively apply Y and ldisapply outlet pressure to said pressure receiving chamber for changing the positions of the piston members in said other bores to thereby determine and control the amount of uid that can flow into the said other bores and to determine and control the amount of fluid that kcan flow past each of said resiliently urged valve means into said discharge chamber and to said outlet whereby to varythe displacement of said pump assembly.

v6. In a pump assembly, the combination of a housing having an inlet and an outlet, -a `pair of cylinder bloc-ks received in said housing `and defining a discharge chamber in communication with said outlet, a plurality of aligned bores in each block, piston means received in each bore, cam ymeans for reciprocating the piston .means in said bores in one of said blocks to pressurize iluid from saidrinlet, resiliently urged valve means for each bore in said one block received in said chamber, passage means in each of :said valve means luidly communicating said respective aligned bores, said passage means allowing a tlow of iluid under pressure vfrom the one aligned bore in said one block Vtothe aligned boregin the other block, means to vary the positions of -the piston means in the bores in the said other bl0l2k,.s aid piston varying means including -a control elemen-t operatively associated with said piston means in the said other block and a control valve means uidly connected to saidroutlet, said control element having a pressure receiving chamber therein, and said control valve means being outlet pressure responsive and being so constructed and arranged to selectively apply and disapply outlet pressure to said pressure receiving chamber for changing the positions of the piston members in said other bores to thereby determine and `control the amount of fluid that can flow into the said other boresand to determine.andgcontrol the amount ojl fluid that can flow -past each of said resiliently urged valve means into :said discharge chamber and to said outlet whereby to vary the displacement of said pump assembly.

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